DE19755873A1 - Arrangement for tolerance compensation in an ink print head - Google Patents

Description

The invention relates to an arrangement for tolerance compensation in a Ink printhead, especially for one of several modules the "non-interlaced" principle composite ink printhead.

Such ink printheads are used both in office printers and in small fast printers - like those for franking machines and pro product labeling devices are required - used and point in the Usually a larger number of nozzles.

A component that specializes in the reliability of a printer the ink printhead is very influential. If the ink print head is composed of several components, has the precise arrangement the same to each other and with each other as well as the ink printing head itself a decisive influence on its safe Function.  

It is known to see "Third Annual European Ink Jet Printing Work shop October 16-18, 1995 Maastricht / Netherlands ", an ink Print head composed of three modules based on the "non-interlaced" principle menzetz, usually by a microprocessor is controlled.

Equal-length, mutually aligned, diagonally running, parallel slots are made in a front plate, into which the modules with their nozzle area are inserted, see also FIG. 1.

The record carrier is moved past the rows of nozzles that the print image is composed of three superimposed strips is set. With a vertical full line, the above is therefore right third of the first module, the middle third of the second Module and the lower third generated by the third module.

However, it is also possible, for example with hand franking seem that the record carrier is at rest and the ink print head is moved, see EP 0 750 277 A2.

Although the slots are usually made with high precision in the front panel and the modules are manufactured as precision parts, tolerance deviations of over a tenth of a millimeter - in a 200 dpi print head with 200 nozzles, this corresponds approximately to the vertical distance between two neighboring nozzles - when changing from one module to the other following, not to be excluded. The error can thereby spacing and parallelism errors and deviations from the line of flight to be within a row of nozzles as well as under-side nozzle, compares for the simplified example of FIG. 1 and FIG. 2.

Fig. 1 shows an error-free nozzle field with the associated Linienab pressure. Three modules 11 , 12 , 13 , each with seven nozzles 111 to 117 , 121 to 127 , 131 to 137, form an ink print head. The nozzles of a nozzle row of a module are arranged equidistantly in a line. Nozzles of the same atomic number, for example the nozzles 111 , 121 , 131 of the modules 11 , 12 , 13 are also arranged equidistantly in a row which is orthogonal to the transport direction of the recording medium 6 . The direction of transport is indicated by the arrow.

In this case, the record carrier 6 is a strip, as is usually used for bulky postal items. The distance Δd of the nozzle with the highest atomic number, for example nozzle 117 of the module 11 , to the nozzle with the lowest atomic number, for example nozzle 121 , of the next module 12 in the direction orthogonal to the transport direction of the recording medium 6 is set so that it is the same Distance between adjacent nozzles of a row of nozzles in the direction mentioned. Δd is, so to speak, the ideal or standard distance.

For the printing of a continuous line 5 orthogonal to the transport direction of the printing medium 6 , nozzles of the same atomic number are actuated at the same time. It starts with the nozzles of the highest ordinal number 117 , 127 , 137. When the recording medium 6 has covered a distance which corresponds to the distance Δs to the next following nozzles 116 , 126 , 136 in the transport direction, the same are actuated. After a path s = 6 × Δs, all twenty-one nozzles 111 to 137 have been actuated once. At constant speed, Δs would correspond to a fixed time interval Δt.

If the conditions described above are complied with, the associated imprint is a continuous straight line 5 composed of twenty-one pressure points 501 to 521 .

Fig. 2 shows a combination of all possible errors of a faulty nozzle field and the associated so-called line print 5. The causes of these errors can on the one hand in manufacturing-related deviations in the length of the individual module - see module 12 - as well as in stress-related bending of the same - see module 11 - and on the other hand, there are manufacturing tolerances of the front panel and its slots - see module 13 -. There would also be errors due to installation tolerances of the ink printhead attachment.

Corresponding deviations from a straight continuous line can then be found in the imprint 5 .

It is already a method of balancing the writing nozzles Ink printhead known in ink writing devices, compare EP 0 257 570 A2. The ink print head is bidi by means of a drive moved rectionally in front of a record carrier. From its individual controllable writing nozzles are according to the one time Chengenerator extracted data during its single movement droplets are ejected at the specified printing times.

According to the method, a printer pre-run takes place during that for each individual writing nozzle separately for each writing direction tung - counterclockwise, clockwise - a defined line pattern on the record is printed.  

A scanning run then takes place during which the line pattern scanned by an optical sensor arranged on the print head which is synchronized to the pressure pulse grid. The samples are in the grid of the print columns of the character matrix as the "actual" position transferred to a central control of the ink writing device.

In the central control, a comparison circuit is used Comparison of the "actual" positions with "target" positions carried out are determined by the corresponding control pulses. The reject Checks between the two positions give the values for the so-called called droplet offset in the grid of the printing columns.

The values for the droplet offset are given for each writing nozzle separately for both writing directions in an additional memory stored in the central control. The droplet offset is ge separates one for the writing directions as a distortion value if the pixel memory contained in the central control continues given.

Each time a writing nozzle is activated in normal printing operation becomes the value of the droplet determined for the relevant writing nozzle offset taken into account depending on the writing direction. To this For this purpose, pre-distortion is used in the preparation of the characters speaking of the printing direction and the determined droplet offset performed.

This solution therefore requires the following for each ink writing device:
an optical scanning sensor, a comparison circuit, two additional memories for the droplet offset storage and two image point memories.

This is a considerable additional effort for a printer.

On top of that comes with this solution in ink printheads that are made from are composed of several modules, tolerances of module too Module cannot be compensated. This is because only one Compensating ahead or lagging on the relative movement line of the writing nozzle is possible.

A franking machine with an ink print head is also known, see EP 0 702 334 A1 and EP 0 702 335 A1, which has a large number of nozzles. The nozzles are arranged in at least two rows arranges that run transversely to the direction of advance of the print carrier. These two rows are along and across the feed direction  offset from each other, so that some first nozzles at the end of a Nozzle row A few second nozzles at the end of the other row of nozzles opposite.

The nozzles in the overlap area are operated alternatively. A Nozzle distance correction is not possible here.

Finally, there is a computer controlled ink jet printing device tion known, see DE 32 36 297 C2, which consists of several ink prints mind exists.

The ink printheads are located one behind the other in the print carrier transport direction the and arranged transversely to the same one above the other. In this way the print image is created according to the "non-interlaced" principle also previous explanations. In each individual ink External memory device assigned to the print head are the image signals nale loaded. When placing them on the ink printheads, a Droplet ejection and thus a printing process triggered. For the Anle The timing of the image signals and control is applied det. Through the control, the image signals are timed in one coordinated ratio to the laterally offset inks printheads created around the different lines in the desired one mutual alignment print. Then the Control a new set of image signals to print the next one Image saved.

The inkjet printing device is with a programmable Mi Croprocessor provided by which the image signals in buffer memories assembled, which are individually assigned to the ink printheads are. The storage of the image signals in the buffers and the subsequent The application to the ink printheads is carried out by means of a central one Timing and control device with a coarse and fine delay Execution device executed. This includes recording the Print media, such as its leading edge, at a specific location on the Transport route and a subsequent timing of the beginning of the Printing process. The distance of the ink printheads from this location is well known, so that during the time interval between pressure carrier detection and the start of the printing process by a Ink printhead an associated buffer with image signals can be loaded. The time interval can be controlled by means of the control can be varied. In this way it can be used by any ink printhead ver created image line on the print carrier to the left or right  be pushed to set the desired location of the line. At least the first pressure column can thus be aligned.

This is analogous to the solution according to EP 0 257 570 Tolerance compensation for installation-related tolerances of the ink printheads possible, but within an inkjet print head from nozzle to nozzle neither. Distance errors between the lines are also hereby not correctable.

The purpose of the invention is to reduce the effort for the verb Print quality improvement.

The invention has for its object an arrangement for Tole ranc compensation for ink printheads of the type mentioned create with both deviations despite reduced effort within a module as well as from module to module and installation Tolerances of the ink print head can be compensated.

According to the invention, this object is achieved according to the main claim solved. Further advantageous features of the invention are the Unteran to take sayings.

By providing each ink printhead with an integrated non-volatile Read-write memory is provided, which its individual Druckda contains the ink printhead before it is installed in the printer electronically pre-balanced. The individual print data included the cycle delay values either module or single nozzle-related gen. Since the ink print head is rotatably mounted, by means of Ver adjusting device a correction from module to module by varying the Installation angle of the ink print head to the transport direction possible. Here too, a mechanical pre-adjustment is carried out before installing the Ink printhead possible. The maximum rotation is that nozzles just overlap in the connection area from module to module cover and then one of them electronically from the printing company is closed. This is not the case with larger numbers of nozzles in the printed image ascertainable and therefore justified.

After installing the ink print head in the printer are necessary still slight installation tolerances by means of the adjustment device comparable.  

The invention is explained in more detail below using the exemplary embodiment explained.

Show it:

Fig. 1 A defect-free nozzle array with the associated line footprint,

Fig. 2 is a remedial exemplary nozzle array with the associated Linienab pressure,

Fig. 3 is a schematic diagram of the arrangement according to the invention,

Fig. 4 shows a schematic diagram of part of the inventive arrangement for the electronic balance,

Fig. 5 shows a nozzle array of FIG. 2 with the corrected line of the impression.

The illustration is for simplification and easier understanding carried out schematically.

Referring to FIG. 3, the arrangement according to the invention from a Tin tendruckkopf 1, a memory 2, an axis 3, and a Verstellein direction 4.

The inkjet print head 1 is composed of three modules 11 , 12 , 13 . The modules 11 , 12 , 13 are arranged one above the other in accordance with the "non-interlaced" principle.

The memory 2 is an integral part of the ink print head 1 and realized as a non-volatile read-write memory by means of an EEPROM. In the memory 2 , individual print data of the ink print head 1 are stored. The individual print data are generated externally before the ink print head is installed in a printing device by evaluating sample prints. The individual print data contain corresponding positive or negative delay values for the clocks for controlling the modules as a whole or the nozzles as individual. The individual data can also be such that a nozzle is excluded from printing.

The inkjet print head 1 is rotatably mounted on the axis 3 within an adjustment area. The bearing for the axis 3 can be formed directly on the housing of the ink print head 1 or indirectly contained in a crossmember for receiving the ink print head 1 .

The adjusting device 4 consists of a threaded bushing 41 , an adjusting screw 42 and a spring 43. It serves to rotate the ink print head 1 within the adjusting area. The ink pressure head 1 is under the action of the spring 43 non-positively on the adjusting screw 42 . The adjusting device 4 can expediently also be fastened on the crossmember mentioned.

. Micro processor - - According to Fig 4 of the store 2 to the pressure control computer 7 is connected via an outgoing data line 75 and a next data line 76 is connected. The first module 11 is connected to the pressure control computer 7 via a clock line 71 and an incoming data line 74 . The second module 12 is connected to the pressure control computer 7 via a clock line 72 . The third module 13 is connected to the pressure control computer 7 via a clock line 73 .

In the case shown, the print data D are entered serially into the modules 11 , 12 , 13 . Therefore, the data line 74 is looped through from the pressure control computer 7 via the module 11 to the module 12 to the module 13 . An alternative is to input the print data D directly to each module via a parallel bus.

The inkjet print head 1 or the modules 11 , 12 , 13 is / are provided in a manner not shown with a commercially available driver circuit with a shift register and latches in front of logic elements. The actuation circuits for the nozzles are triggered in accordance with the time and image information by means of the logic links on which the assigned clock lines with the corrected clocks T1 to T3 are applied.

The print control computer 7 is connected to a scanner 8 via a signal line 81 for generating the correction data or the individual print data I. Be at a first Pro Imprinted gaps in the impression 5, as the building facing via the standard .DELTA.d rising height offset v between Dot 514 and 515, is detected, the ink jet head 1 is rotated so far left about in this case is made up of the connection in the vertical direction . The angle of rotation is already mechanically saved with the rotation of the adjusting screw 42 .

The newly generated impression 5 is scanned and the scanning signals As are fed to the pressure control computer 7 in relation to the dot or nozzle. The scanning signals As are compared in the pressure control computer 7 with standard values already stored therein, and the deviations are converted into signed correction data I and entered into the memory 2 via the data line 76 in an address-related manner. However, it is also possible to dispense with the sign part if only delay values are generated with respect to the most lagging dot, for example dot 515 or 521 in FIG. 2. In this case, the offset v in the transport direction from module 13 to module 12 is somewhat smaller than the corresponding nozzle spacing Δs.

The correction data or individual print data I are loaded into the memory 2 via the data line 76 . The ink print head 1 is thus also electronically adjusted.

After the final installation of the ink printhead 1 in a printing device, the individual print data I are accessed via the data line 75 by the microprocessor 7 from the EEPROM 2 and incorporated in the generation of the clocks T1, T2, T3.

FIG. 5 shows a line imprint corrected according to the procedure described above for the faulty nozzle field according to FIG. 2. In this case, the nozzle 121 is electronically blocked for printing.

Reference list

1

Ink printhead

11

first module

111

to

117

Nozzles of the first module

12th

second module

121

to

127

Second module nozzles

13

third module

131

to

137

Third module nozzles

2nd

Memory, EEPROM, non-volatile

3rd

axis

4th

Adjustment device

41

Threaded bush

42

Adjusting screw

43

feather

5

Footprint

501

to

507

Dots or pressure points from the first module

11

generated

508

to

514

Dots or pressure points from the second module

12th

generated

515

to

521

Dots or pressure points from the third module

13

generated

6

Record carriers, printing strips

7

Pressure control computer, microprocessor

71

Clock line to the first module

11

72

Clock line to the second module

12th

73

Clock line to the third module

13

74

Data line to the modules

11

,

12th

,

13

75

Data line from the printhead-internal memory

2nd

to the microprocessor

7

76

Data line to the print head internal memory

2nd

8th

scanner

81

Signal line
As scanning signals from the scanner to the microprocessor

7

D Print data for the modules

11

,

12th

,

13

Δd standard nozzle offset orthogonal to the transport direction
I individual print data, correction data
Δs standard nozzle offset in the direction of transport
s Row length of nozzle in the direction of transport
T1 clock for module

11

T2 clock for module

12th

T3 clock for module

13

v Module offset in the direction of transport

Claims (5)

1. Arrangement for tolerance compensation in an ink print head, in particular in an ink print head composed of several modules according to the "non-interlaced" principle and controlled by a print control computer, characterized in that
that a memory (2) is integrated in the ink print head (1), in which individual print data (1) of the ink print head (1) are stored, the external means of evaluation of sample placing, before mounting the ink print head (1) in a pressure device that generates be and
that the ink print head ( 1 ) is rotatably mounted about an axis ( 3 ) within an adjustment area and for the mechanical adjustment of the ink print head ( 2 ) an adjusting device ( 4 ) is provided. 2. Arrangement according to claim 1, characterized in that in the memory ( 2 ), the individual print data ( 1 ) for each individual nozzle ( 111 to 117 , 121 to 127 , 131 to 137 ) are stored. 3. Arrangement according to claim 1, characterized in that in the memory ( 2 ) the individual print data ( 1 ) for each an individual module ( 11 , 12 , 13 ) are stored. 4. Arrangement according to claim 1, characterized in that the memory ( 2 ) is designed as a non-volatile read-write memory by means of an EEPROM. 5. Arrangement according to claim 1, characterized in that the adjusting device ( 4 ) from a threaded bush ( 41 ), a guided in the same adjusting screw ( 42 ) and a spring ( 43 ) be, the threaded bush ( 41 ) is fixed in the printer and the ink print head ( 1 ) under the action of the spring ( 43 ) non-positively against the adjusting screw ( 42 ).